How is old M7/M8 data handled in Health app?

With iOS 8, I've been wondering how is handled the old data given by the M7/M8?

These coprocessors can only keep a week or two full of data, and then it's erased.
So for anyone who ran the iOS 8 beta, what happens after some weeks? Is old data written as from "Health" and not "My iPhone"?

Also, does anyone know if the samples are compiled after some amount of time?
On my iPhone 5s, there are around 5000-6000 samples just in the step counter for 1 week. It already takes 7-8 seconds to load, and it's impossible to check how many steps I walked on a particular day.
I'm really scared of what will happen in a month if data aren't compiled regularly... (as it is very small increments)
Does anyone have knowledge about that too? Or is it a design flaw?

With iOS 8, I've been wondering how is handled the old data given by the M7/M8?

These coprocessors can only keep a week or two full of data, and then it's erased.
So for anyone who ran the iOS 8 beta, what happens after some weeks? Is old data written as from "Health" and not "My iPhone"?

Also, does anyone know if the samples are compiled after some amount of time?
On my iPhone 5s, there are around 5000-6000 samples just in the step counter for 1 week. It already takes 7-8 seconds to load, and it's impossible to check how many steps I walked on a particular day.
I'm really scared of what will happen in a month if data aren't compiled regularly... (as it is very small increments)
Does anyone have knowledge about that too? Or is it a design flaw?

If it works like the fitbit Flex & fitbit App then it'll just write the data to the health app then overwrite what's on the M7/M8 Chip, as I don't have an iPhone with an M7/M8 Coprocessor only an iPhone 4S & fitbit Flex I'm just making assumptions on how it'll work. But as fitness wristbands e.t.c. work like the M7/M8 Chips but in an external case with battery then I can't see why the M7/M8 wouldn't work the same.

Thanks for your post and for bringing up the idea it could overwrite the M7/M8's data after gathering the data. I couldn't have thought of this.
With this in mind, I tried this :

1. Launch the Health app and let the data be gathered.
2. Download and Launch a Pedometer app, using solely M7/M8 data (it's basically an app to read what's stored in M7/M8).

At this step, the Pedometer app still shows the data from M7/M8, so it's not erased after Health read it.

3. Go back to Health and delete some samples.
4. Delete and re-download a fresh Pedometer app.

The Pedometer app still shows the same number of steps. Therefore, deleting samples in the Health app doesn't delete data in the M7/M8.

5. Go back in the Health app and check the data.

The data is unchanged. What I mean is the deleted samples are not sync'd back, even though they're still on the M7/M8 chip.

These are my conclusions up to now. However, I'm still really wondering what happens to all the old samples, if they're combined automatically or not... Because I have an indecent number of samples already, most of them with a small increments (like 5 steps at a time, and not 200, making the number of samples be incredibly huge).

If anyone had more info about how old samples are handled, or just general knowledge about the Health app, I'd love to hear from you!